JP2535926B2 - Image transmission method - Google Patents

Description

The present invention relates to a transmission method for transmitting and receiving image data via a transmission line such as a public line.

[Conventional technology]

The image transmission device basically comprises a transmitter that compresses image information and sends it out to a transmission line, and a receiver that receives compressed image data from the transmission line and expands it. Normally, the transmission procedure shown in FIG. adopt. First, the transmission block size of the image data to be transmitted is determined. Next, this transmission block
In size, the transmitter sends the image data to the transmission line. At the time of transmission, as shown in FIG. 6, before the data body,
A block number for identifying a transmission block is added, and an error check code is added after the data body.

The receiver checks the error check code of the received block after receiving all blocks or after receiving each block,
Tell the transmitter the number of the block in error. The transmitter retransmits the data of the block in which the error has occurred, and ends the image transmission when the transmission error is eliminated.

[Problems to be solved by the invention]

In the conventional transmission device, one screen data of a × b pixels is vertically divided into N blocks as shown in FIG. 4, and each block is framed and transmitted as shown in FIG. Was there. Then, this N is changed according to the quality of the transmission path.

As the image compression method, a method using only one-dimensional predictive coding, and one-dimensional predictive coding for the first line and two-dimensional predictive coding for the second and subsequent lines for each block unit are used. There is a way to do it. In the former method, the amount of compressed data does not change depending on N, and therefore the compression efficiency is constant regardless of N, but the latter method has better overall compression efficiency than the former method, but the number of blocks As N becomes larger, the number of lines for one-dimensional prediction increases, so that the compression efficiency becomes worse. Therefore, as N becomes larger, the image transmission time becomes longer.

Therefore, it is an object of the present invention to provide an image transmission method capable of efficiently transmitting image data in a short time without lowering the image compression efficiency.

[Means for solving problems]

The image transmission method according to the present invention divides an image into a plurality of blocks containing one or more line data, compresses each block, and compresses each line of the compressed data according to the quality of the transmission path. It is characterized in that each pixel number obtained by dividing by the integer value M is framed and transmitted.

[Action]

In the present invention, the data of one screen is divided into a plurality of blocks having one or more line data, and compression is performed for each block, so that the image compression rate becomes constant regardless of the error rate of the transmission path. . Further, by framing the data of each line to be transmitted for each pixel number divided by M, the data amount of the transmission unit reflects the quality of the transmission path, and therefore the overall transmission time is reduced. It can be kept short and image data can be transmitted efficiently.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. In the present invention, as in FIG. 4, the screen composed of a × b pixels is divided in the vertical direction by a constant division number N regardless of the quality of the transmission path, and divided into N blocks. For each block,
As shown in FIG. 1, one-dimensional predictive coding is performed on the data of the first line, and two-dimensional predictive coding is performed on the other lines. However, the data amount of one transmission frame is determined by dividing each line by the division number M according to the quality of the transmission path. This M is 1 when the quality of the transmission line is the best.
Is.

Further, in the present invention, data is transmitted line by line for each of the N blocks. That is, when M is 1, 1
Data of b pixels for a line are collectively transmitted in one frame, and when M is 2 or more, b /
Each of the M pixels is framed and sent M times to send b pixel data of the target line. After that, data is similarly sent to the next line.

Fig. 2 shows when the quality of the transmission line is the best (that is, M = 1).
Shows the frame format of. Hereinafter, this is called a large frame. This frame 10 has a block number 12 indicating which block out of N blocks and a line number 14 indicating which line in the block.
And the data body 16 for b pixels and the error of that data.
It consists of check code 18.

In this large frame transmission, the first frame to be transmitted consists of the block number, the number of the first line (for example, 1), the data of the first line, and the check code thereof, and is then transmitted. The frame is
It consists of the same block number as before, the number of the second line (for example, 2), the data of the second line, and its check code. Thereafter, similarly, data for one block is transmitted, and finally, data for all blocks is transmitted.

Next, the case where the quality of the transmission path is poor and the number of pixels in the transmission unit is reduced (M> 1) will be described. However, even in this case, the vertical division number N is constant. In this case, the data amount of the transmission unit is b / M pixels, and the transmission frame (hereinafter referred to as small frame) 20 of FIG. 3 is adopted. In this small frame 20, a line division number 26 indicating which division position of the horizontal M division data is added is added. In this order, the block number 22, the line number 24 in the corresponding block, and the above Line division number 26, b / M pixel data 2
8 and its check code 30.

Even in the case of this small frame, the present invention transmits data line by line. That is, when the data of a certain line is to be transmitted, the data of the leftmost b / M pixel on the line in FIG. 1 is first converted into a small frame and transmitted. The line division number 26 at this time is 1, for example. In the next frame, the data of the next b / M pixel on the same line is transmitted. The line division number 26 at this time is 2.
When the transmission of the b-pixel data for one line is completed in this way, the data for the next line is transmitted. After transmitting the data of all the lines of one block, the data of the next block is transmitted.

On the receiver side, the presence or absence of an error is checked for each frame, and data is retransmitted in units of this frame. This data may be retransmitted every block, every screen, or every time an erroneous frame is received. That is, in the present invention, the procedure of retransmission at the time of error may be the general procedure of FIG. 5 or another procedure.

When CRC is used for the check code of the large frame and the small frame in the above embodiment, the data length is different, so the CRC length can be increased or decreased according to the data length. For example, in a small frame, the CRC length can be shortened to improve data redundancy. Further, in the present embodiment, the frame format has a block number, a line number, and a line division number. However, a number is given to a presumed minimum division, and the given number may be used at any time. Good.

〔The invention's effect〕

As can be easily understood from the above description, according to the present invention, it is possible to perform data transmission according to the quality of the transmission path while keeping the image compression rate constant, and thus complete the transmission in a short time. sell. Also, since the image data is framed in the line direction, when the receiver side decodes the image data, if compressed data without error is received in the first line of each block, the image is sequentially read from the upper line. The data can be decrypted. As a result, the time from the reception of the compressed code to the decoding of the compressed code is shortened. Further, when performing the filtering process on the decoded data, the image data in the horizontal direction is aligned from the upper line, and therefore the time from the reception of the image to the end of the filtering process is shortened.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of blocking and transmission units in one embodiment of the present invention, FIG. 2 is a structural diagram of a large frame of the embodiment of the present invention, and FIG. 3 is a small frame of the embodiment of the present invention. FIG. 4 is an explanatory view of a state in which the screen is divided in the vertical direction and divided into N blocks, FIG. 5 is an explanatory view of a general transmission procedure of image data, and FIG. 6 is a conventional transmission. It is a structure explanatory drawing of a format.

Claims (1)

(57) [Claims] 1. An image is divided into a plurality of blocks containing one or more line data, and image compression is performed for each block.
An image transmission method characterized by dividing each line of the compressed data by an integer value M corresponding to the quality of the transmission path to form a frame for each number of pixels obtained and transmitting.